#include <iostream>

using namespace std;

int F[1000];

int main()
{
	int n;
	cin >> n;
	F[1] = F[2] = 1;

	for(int i = 3; i <= n; i++) {
		F[i] = F[i-1] + F[i-2];
	}

	cout << F[n] << endl;

	return 0;
}